The appearances, when only a small dose has been taken, are not unlike those of asphyxia. The detection of the odour of hydrocyanic acid in the body is of importance; but this may be absent from the following causes:
1. Smallness of the quantity of the acid present.
2. Volatilisation from exposure of the corpse to the air.
3. The smallness of the dose, and its absence the result of absorption and elimination, if death has not rapidly taken place.
4. The amount of dilution of the poison.
5. Concealed by other odorous substances.
In some cases, the smell may be detected in the stomach seven or eight days after death. The viscera should, in all cases of suspected poisoning, be placed in a glass-stoppered jar, and the stopper covered by bladder and tinfoil. Hydrocyanic acid is so volatile that, unless the greatest care be taken, all traces of it may vanish; and thus the guilty person may be allowed to escape.
Fatal Period.—From a few seconds to as many minutes. Under active treatment, if a patient survive forty minutes, he will generally recover.
Fatal Dose.—Thirty minims of the dilute acid of the Pharmacopœia. This contains six-tenths of a grain of the anhydrous acid. Recovery has, however, taken place even after comparatively large doses. The strength and age of the individual, and also the emptiness or fulness of the stomach at the time the poison is swallowed, will materially affect the issue.
Experiments on Animals